Clinical profiles of post-load glucose subgroups and their association with glycaemic traits over time: An IMI-DIRECT study

AIM

To examine the hypothesis that, based on their glucose curves during a seven-point oral glucose tolerance test, people at elevated type 2 diabetes risk can be divided into subgroups with different clinical profiles at baseline and different degrees of subsequent glycaemic deterioration.

METHODS

We included 2126 participants at elevated type 2 diabetes risk from the Diabetes Research on Patient Stratification (IMI-DIRECT) study. Latent class trajectory analysis was used to identify subgroups from a seven-point oral glucose tolerance test at baseline and follow-up. Linear models quantified the associations between the subgroups with glycaemic traits at baseline and 18 months.

RESULTS

At baseline, we identified four glucose curve subgroups, labelled in order of increasing peak levels as 1-4. Participants in Subgroups 2-4, were more likely to have higher insulin resistance (homeostatic model assessment) and a lower Matsuda index, than those in Subgroup 1. Overall, participants in Subgroups 3 and 4, had higher glycaemic trait values, with the exception of the Matsuda and insulinogenic indices. At 18 months, change in homeostatic model assessment of insulin resistance was higher in Subgroup 4 (β = 0.36, 95% CI 0.13-0.58), Subgroup 3 (β = 0.30; 95% CI 0.10-0.50) and Subgroup 2 (β = 0.18; 95% CI 0.04-0.32), compared to Subgroup 1. The same was observed for C-peptide and insulin. Five subgroups were identified at follow-up, and the majority of participants remained in the same subgroup or progressed to higher peak subgroups after 18 months.

CONCLUSIONS

Using data from a frequently sampled oral glucose tolerance test, glucose curve patterns associated with different clinical characteristics and different rates of subsequent glycaemic deterioration can be identified.

Effect of metformin on plasma metabolite profile in the Copenhagen Insulin and Metformin Therapy (CIMT) trial

AIM

Metformin is the first-line treatment for Type 2 diabetes. However, not all people benefit from this drug. Our aim was to investigate the effects of metformin on the plasma metabolome and whether the pretreatment metabolite profile can predict HbA_1c outcome.

METHODS

Post hoc analysis of the Copenhagen Insulin and Metformin Therapy (CIMT) trial, a multicentre study from May 2008 to December 2012, was carried out. We used a non-target method to analyse 87 plasma metabolites in participants with Type 2 diabetes (n = 370) who were randomized in a 1 : 1 ratio to 18 months of metformin or placebo treatment. Metabolites were measured by liquid chromatography-mass spectrometry at baseline and at 18-month follow-up and the data were analysed using a linear mixed-effect model.

RESULTS

At baseline, participants who were on metformin before the trial (n = 312) had higher levels of leucine/isoleucine and five lysophosphatidylethanolamines (LPEs), and lower levels of carnitine and valine compared with metformin-naïve participants (n = 58). At follow-up, participants randomized to metformin (n = 188) had elevated levels of leucine/isoleucine and reduced carnitine, tyrosine and valine compared with placebo (n = 182). At baseline, participants on metformin treatment with the highest levels of carnitine C10:1 and leucine/isoleucine had the lowest HbA_1c (P-interaction = 0.02 and 0.03, respectively). This association was not significant with HbA_1c at follow-up.

CONCLUSIONS

Metformin treatment is associated with decreased levels of valine, tyrosine and carnitine, and increased levels of leucine/isoleucine. None of the identified metabolites can predict the HbA_1c -lowering effect of metformin. Further studies of the association between metformin, carnitine and leucine/isoleucine are warranted.

Cost-effectiveness of sensor-augmented pump therapy versus standard insulin pump therapy in patients with type 1 diabetes in Denmark

AIMS

The use of continuous subcutaneous insulin infusion (CSII) in type 1 diabetes (T1D) has increased in recent years. Sensor-augmented pump therapy (SAP) with low glucose suspend (LGS) (allowing temporary suspension of insulin delivery if blood glucose level falls below a pre-defined threshold level) provides additional benefits over CSII alone, but is associated with higher acquisition costs. Therefore, a cost-effectiveness analysis of SAP+LGS versus CSII in patients with T1D was performed.

METHODS

Analyses were performed using the CORE Diabetes Model in two different patient cohorts in Denmark, one with hyperglycemia at baseline and one with increased risk for hypoglycemic events. Clinical input data were sourced from published literature. The analysis was performed over a lifetime time horizon from a societal perspective. Future costs and clinical outcomes were discounted at 3% per annum.

RESULTS

In patients who were hyperglycemic at baseline the use of SAP+LGS versus CSII resulted in improved quality-adjusted life expectancy (12.44 versus 10.99 quality-adjusted life years [QALYs]) but higher mean lifetime costs (DKK 2,027,316 versus DKK 1,801,293) leading to an incremental cost-effectiveness ratio (ICER) of DKK 156,082 per QALY gained. For patients at increased risk for hypoglycemic events the ICER for SAP+LGS versus CSII was DKK 89,868 per QALY gained.

CONCLUSIONS

The ICER for SAP+LGS versus CSII falls below commonly cited willingness-to-pay thresholds. Therefore, in Denmark, the use of SAP+LGS is likely to be considered cost-effective relative to CSII for patients with T1D who are either hyperglycemic, despite CSII use, or who experience frequent severe hypoglycemic events.

Metabolite profiling of obese individuals before and after a one year weight loss program

OBJECTIVE

We and others have previously characterized changes in circulating metabolite levels following diet-induced weight loss. Our aim was to investigate whether baseline metabolite levels and weight-loss-induced changes in these are predictive of or associated with changes in body mass index (BMI) and metabolic risk traits.

METHODS

Serum metabolites were analyzed with gas and liquid chromatography/mass spectrometry in 91 obese individuals at baseline and after participating in a 1 year non-surgical weight loss program.ResultsA total of 137 metabolites were identified and semi-quantified at baseline (BMI 42.7±5.8, mean±s.d.) and at follow-up (BMI 36.3±6.6). Weight-loss-induced modification was observed for levels of 57 metabolites in individuals with ⩾10% weight loss. Lower baseline levels of xylitol was predictive of a greater decrease in BMI (β=0.06, P<0.01) and ⩾10% weight loss (odds ratio (OR)=0.2, confidence interval (CI)=0.07-0.7, P=0.01). Decreases in levels of isoleucine, leucine, valine and tyrosine were associated with decrease in BMI (β>0.1, P<0.05) and ⩾10% weight loss (isoleucine: OR=0.08, CI=0.01-0.3, leucine: OR=0.1, CI=0.01-0.6, valine: OR=0.1, CI=0.02-0.5, tyrosine: OR=0.1, CI=0.03-0.6, P<0.02).

CONCLUSIONS

Diet-induced weight loss leads to mainly reduced levels of metabolites that are elevated in obese insulin resistant individuals. We identified multiple new associations with metabolic risk factors and validated several previous findings related to weight loss-mediated metabolite changes. Levels of specific metabolites, such as xylitol, may be predictive of the response to non-surgical weight loss already at baseline.

High and low vitamin D level is associated with cardiovascular autonomic neuropathy in people with Type 1 and Type 2 diabetes

AIM

To investigate the possible association between vitamin D deficiency and cardiovascular autonomic neuropathy in people with diabetes.

METHODS

A total of 113 people with Type 1 or Type 2 diabetes [mean (interquartile range) diabetes duration 22.0 (12-31) years, mean (sd) age 56.2 (13.0) years, 58% men] underwent vitamin D (D2 and D3) assessment, and were screened for cardiovascular autonomic neuropathy using three cardiovascular reflex tests [heart rate response to deep breathing (E/I ratio), to standing (30/15 ratio) and to the Valsalva manoeuvre] and assessment of 5-min resting heart rate and heart rate variability indices.

RESULTS

We found an inverse U-shaped association between serum vitamin D level and E/I ratio, 30/15 ratio and three heart rate variability indices (P < 0.05). Vitamin D level was non-linearly associated with cardiovascular autonomic neuropathy diagnosis (P < 0.05 adjusted for age and sex). Linear regression models showed that an increase in vitamin D level from 25 to 50 nmol/l was associated with an increase of 3.9% (95% CI 0.1;7.9) in E/I ratio and 4.8% (95% CI 4.7;9.3) in 30/15 ratio. Conversely, an increase from 125 to 150 nmol/l in vitamin D level was associated with a decrease of 2.6% (95% CI -5.8;0.1) and 4.1% (95% CI -5.8;-0.5) in the respective outcome measures.

CONCLUSIONS

High and low vitamin D levels were associated with cardiovascular autonomic neuropathy in people with diabetes. Future studies should explore this association and the efficacy of treating dysvitaminosis D to prevent cardiovascular autonomic neuropathy.

Potential positive impact of group-based diabetes dialogue meetings on diabetes distress and glucose control in people with type 1 diabetes

OBJECTIVE

To evaluate the effect of group-based diabetes dialogue meetings (DDMs) on diabetes distress, perceived competence and glycaemic control.

METHODS

Patients with type 1 diabetes (T1D) were invited to DDMs with peers and healthcare professionals. The impact of participation was evaluated by change in diabetes distress measured by Problem Areas in Diabetes (PAID), diabetes competence measured by Perceived Competence in Diabetes (PCD), change in HbA1c before and one year after the DDMs.

RESULTS

120 patients with T1D participated in at least one DDM: 75% female, mean age 50 years (range 21-76), mean diabetes duration 23 years (range 0-64); 39% of all participants had a baseline PAID score≥33, indicating high levels of distress. After one year, both PAID (from 30.4±16.6 to 27.4±17.1; n=81, p=0.03), and mean HbA1c (61.6±10.2 to 58.8±9.9; n=120, p<0.0001) had improved significantly. PCD showed no change. Meanwhile, the benefit from participating was rated high with a median of four out of five and the major gain being the possibility to share experiences with peers.

CONCLUSION

Group-based DDMs were highly appreciated by participants and associated with significant improvements in diabetes distress and HbA1c.

PRACTICE IMPLICATIONS

DDMs target a large group of patients using few staff resources.

Vitamin D insufficiency over 5 years is associated with increased fracture risk-an observational cohort study of elderly women

This study of elderly Swedish women investigated the association between chronic vitamin D insufficiency and osteoporotic fractures occurring between ages 80-90. The incidence and risk of hip and major osteoporotic fractures was significantly higher in elderly women with low vitamin D levels maintained over 5 years.

INTRODUCTION

Vitamin D insufficiency among the elderly is common; however, relatively little is known about the effects of long-term hypovitaminosis D on fracture. We investigated sequential assessment of serum 25(OH)D at age 75 and 80 to determine if continuously low 25(OH)D levels are associated with increased 10-year fracture incidence.

METHODS

One thousand forty-four Swedish women from the population-based OPRA cohort, all 75 years old, attended at baseline (BL); 715 attended at 5 years. S-25(OH)D was available in 987 and 640, respectively and categorized as: <50 (Low), 50-75 (Intermediate), and >75 nmol/L (High). Incident fracture data was collected with maximum follow-up to 90 years of age.

RESULTS

Hip fracture incidence between age 80-85 was higher in women who had low 25(OH)D at both baseline and 5 years (22.2 % (Low) vs. 6.6 % (High); p = 0.003). Between age 80-90, hip fracture incidence was more than double that of women in the high category (27.9 vs. 12.3 %; p = 0.006). Within 5-years, 50 % of women in the continuously low group compared to 34 % in the continuously high 25(OH)D group had an osteoporotic fracture (p = 0.004) while 10-year incidence was higher compared to the intermediate (p = 0.020) but not the high category (p = 0.053). The 10-year relative risk of hip fracture was almost three times higher and osteoporotic fracture risk almost doubled for women in the lowest 25(OH)D category compared to the high category (HR 2.7 and 1.7; p = 0.003 and 0.023, respectively).

CONCLUSION

In these elderly women, 25(OH)D insufficiency over 5-years was associated with increased 10-year risk of hip and major osteoporotic fractures.

Six-minute walk test before and after a weight reduction program in obese subjects

OBEJCTIVE: Weight loss and physical activity have shown favorable effects on risks associated with obesity. It is therefore of interest to evaluate exercise capacity and related co-morbidities in obese patients.

DESIGN AND METHODS

We present data from obese subjects evaluated by the 6-minute walk test (6MWT) before and after a 7.3 (6.1-8.2) month weight reduction program.

RESULTS

251 subjects completed the test at baseline (BMI 40.6 [36.9-44.6] kg/m(2) ) and 129 (51.4%) repeated the test after intervention (BMI 35.6 [31.2-38.5] kg/m(2) ). The six minute walking distance (6MWD) at baseline (535 [480-580] m) and at follow up (599 [522-640] m) correlated to several cardiovascular risk markers. Age, weight, height, resting heart rate, smoking status, fP-glucose and use of β-blockers explained 43 % of the variance in predicted 6MWD at baseline. The effect of smoking status, fP-glucose, β-blockers, and resting heart rate lost significance at follow up. Presence of diabetes and the metabolic syndrome had a negative influence on 6MWD but did not affect the impact of intervention based on percentage increase in walking distance. Gender had no impact on 6MWD. Reported pain during the test was common but decreased after intervention (57.0% vs. 28.7%, P < 0.001).

CONCLUSIONS

The 6MWT may be used to evaluate intervention success beyond kilogram weight loss in obese subjects. We present formulas to predict 6MWD and the effect of weight loss on walking distance in clinical practice. Pain is a common problem which has to be considered when giving advice on exercise as a part of weight loss intervention.

Willingness-to-pay for benefits associated with basal insulin treatment of type 2 diabetes

Data from a 20-week trial comparing insulin detemir and neutral protamine Hagedorn (NPH) insulin in insulin-naïve people with type 2 diabetes were analyzed using willingness-to-pay (WTP) data, a proxy for patient preference. The advantages of insulin detemir relative to NPH insulin with respect to a lower hypoglycemia rate and less weight gain were associated with a value of €27.87 per month.

Willingness to pay for diabetes drug therapy in type 2 diabetes patients: based on LEAD clinical programme results

OBJECTIVE

The purpose of this study was to investigate the preferences of people with diabetes for liraglutide vs other glucose lowering drugs, based on outcomes of clinical trials.

METHODS

Willingness to pay (WTP) for diabetes drug treatment was assessed by combining results from a recent WTP study with analysis of results from the Liraglutide Effect and Action in Diabetes (LEAD) programme. The LEAD programme included six randomised clinical trials with 3967 participants analysing efficacy and safety of liraglutide 1.2 mg (LEAD 1-6 trials), rosiglitazone (LEAD 1 trial), glimepiride (LEAD 2-3 trials), insulin glargine (LEAD 5 trial), and exenatide (LEAD 6 trial). The WTP survey used discrete choice experimental (DCE) methodology to evaluate the convenience and clinical effects of glucose lowering treatments.

RESULTS

People with type 2 diabetes were prepared to pay an extra €2.64/day for liraglutide compared with rosiglitazone, an extra €1.94/day compared with glimepiride, an extra €3.36/day compared with insulin glargine, and an extra €0.81/day compared with exenatide. Weight loss was the largest component of WTP for liraglutide compared with rosiglitazone, glimepiride, and insulin glargine. Differences in the administration of the two drugs was the largest component of WTP for liraglutide (once daily anytime) compared with exenatide (twice daily with meals). A limitation of the study was that it was based on six clinical trials where liraglutide was the test drug, but each trial had a different comparator, therefore the clinical effects of liraglutide were much better documented than the comparators.

CONCLUSIONS

WTP analyses of the clinical results from the LEAD programme suggested that participants with type 2 diabetes were willing to pay appreciably more for liraglutide than other glucose lowering treatments. This was driven by the relative advantage of weight loss compared with rosiglitazone, glimepiride, and insulin glargine, and administration frequency compared with exenatide.

Willingness to pay for health improvements associated with anti-diabetes treatments for people with type 2 diabetes

OBJECTIVES

This study aimed to investigate the most important consequences of diabetes medication, as measured by the patients' willingness to pay (WTP).

RESEARCH DESIGN AND METHODS

People in Sweden were recruited using existing nationwide e-mail panels if they were adults (>or=18 years) with type 2 diabetes and were receiving pharmacological anti-diabetes treatment(s). Data were collected electronically and results were analysed using a standard statistical model designed for choice games (conditional logit). Six characteristics relating to treatment of diabetes were examined: weight (gain or loss), mean glycated haemoglobin level (HbA(1c)), hypoglycaemic events, nausea, need for injections (with or independently of meals), and blood glucose testing.

RESULTS

A total of 461 people with type 2 diabetes (291 males; 170 females) completed an internet questionnaire and were eligible for inclusion. Participants placed high value on weight loss and nausea avoidance; they would pay 176 Swedish Krona (SEK)/euro15.61 per month to lose 1 kg, and would pay SEK 560 (euro49.67) per month to avoid nausea completely. Patients wanting to reduce the number of hypoglycaemic events from three per month to none were willing to pay SEK 419 (euro37.17) per month. Patients valued a 1 percentage point reduction in HbA(1c) at SEK 414 (euro36.72) per month. Participants preferred taking tablets to injections and required a compensation of SEK 376 (euro33.35) to accept one injection/day. Injections independent of meals were preferred to injections with meals (WTP: SEK 140/euro12.42 per month). Potential limitations of this study are that the preferences expressed may not match preferences in real-life situations, and bias through the use of electronic questionnaire, which restricted participation to those with access to, and experience with, the internet.

CONCLUSION

People with type 2 diabetes were willing to pay a considerable amount of money each month to lose weight, reduce or avoid hypoglycaemic events and reduce HbA(1C).

A common variant in PNPLA3, which encodes adiponutrin, is associated with liver fat content in humans

AIMS/HYPOTHESIS

It has recently been suggested that the rs738409 G allele in PNPLA3, which encodes adiponutrin, is strongly associated with increased liver fat content in three different ethnic groups. The aims of the present study were as follows: (1) to try to replicate these findings in European individuals with quantitative measures of hepatic fat content; (2) to study whether the polymorphism influences hepatic and adipose tissue insulin sensitivity; and (3) to investigate whether PNPLA3 expression is altered in the human fatty liver.

METHODS

We genotyped 291 Finnish individuals in whom liver fat had been measured using proton magnetic resonance spectroscopy. Hepatic PNPLA3 expression was measured in 32 participants. Hepatic and adipose tissue insulin sensitivities were measured using a euglycaemic-hyperinsulinaemic (insulin infusion 0.3 mU kg(-1) min(-1)) clamp technique combined with infusion of [3-(3)H]glucose in 109 participants.

RESULTS

The rs738409 G allele in PNPLA3 was associated with increased quantitative measures of liver fat content (p = 0.011) and serum aspartate aminotransferase concentrations (p = 0.002) independently of age, sex and BMI. Fasting serum insulin and hepatic and adipose tissue insulin sensitivity were related to liver fat content independently of genotype status. PNPLA3 mRNA expression in the liver was positively related to obesity (r = 0.62, p < 0.0001) and to liver fat content (r = 0.58, p = 0.025) in participants who were not morbidly obese (BMI < 40 kg/m(2)).

CONCLUSIONS/INTERPRETATION

A common variant in PNPLA3 increases the risk of hepatic steatosis in humans.

A polymorphism in the adiponectin gene influences adiponectin expression levels in visceral fat in obese subjects

OBJECTIVE

Reduced serum adiponectin levels have been found in obesity and type 2 diabetes and variations in the adiponectin gene (APM1) have been associated with type 2 diabetes and features of the metabolic syndrome in different populations.

STUDY DESIGN

Here, we investigated the expression of APM1 in adipose tissue and studied the relationship between variation in APM1 expression, the APM1 G276T polymorphism, the common PPARG Pro12Ala polymorphism and clinical features of 36 morbidly obese (body mass index (BMI) 41.5 +/- 4.9 kg/m2) nondiabetic subjects.

RESULTS

APM1 mRNA expression in visceral fat was correlated with serum adiponectin levels (r = 0.54, P = 0.012). In visceral, but not in subcutaneous, adipose tissue APM1 mRNA level was 38% higher among carriers of the APM1 G276T T allele (G/T and T/T) than among carriers of the G/G genotype (0.91 +/- 0.06 for G/T and T/T carriers vs 0.66 +/- 0.09 for G/G carriers, P = 0.013). Carriers of the T allele also had significantly higher body fat percent compared to G/G carriers (65 +/- 6 vs 56 +/- 10%, P = 0.011).

CONCLUSION

Our results indicate that genetic variation in APM1 influences the expression of the gene in visceral adipose tissue and suggest a potential role for such variation in regulation of body fat accumulation in obese subjects.

The hormone-sensitive lipase C-60G promoter polymorphism is associated with increased waist circumference in normal-weight subjects

OBJECTIVE

Hormone-sensitive lipase (HSL) is a key enzyme in the mobilization of fatty acids from triglyceride stores in adipocytes. The aim of the present study was to investigate the role of the HSL gene promoter variant C-60G, a polymorphism which previously has been associated with reduced promoter activity in vitro, in obesity and type 2 diabetes.

DESIGN

We genotyped two materials consisting of obese subjects and non-obese controls, one material with offspring-parents trios, where the offspring was abdominally obese and one material with trios, where the offspring had type 2 diabetes or impaired glucose homeostasis. HSL promoter containing the HSL C-60G G-allele was generated and tested against a construct with the C-allele in HeLa cells and primary rat adipocytes. HSL mRNA levels were quantified in subcutaneous and visceral fat from 33 obese subjects.

RESULTS

We found that the common C-allele was associated with increased waist circumference and WHR in lean controls, but there was no difference in genotype frequency between obese and non-obese subjects. There was a significant increased transmission of C-alleles to the abdominally obese offspring but no increased transmission of C-alleles was observed to offspring with impaired glucose homeostasis. The G-allele showed reduced transcription in HeLa cells and primary rat adipocytes. HSL mRNA levels were significantly higher in subcutaneous compared to visceral fat from obese subjects.

CONCLUSION

The HSL C-60G polymorphism is associated with increased waist circumference in non-obese subjects.

Increased risk of obesity associated with the variant allele of the PPARGC1A Gly482Ser polymorphism in physically inactive elderly men

AIMS/HYPOTHESIS

The variant allele of the Gly482Ser polymorphism in peroxisome proliferator-activated receptor-gamma co-activator-1alpha (PPARGC1A or PGC1alpha), a critical determinant of skeletal muscle metabolism, has been associated with obesity and type 2 diabetes. Previous studies indicate that these risks depend on sex and environmental triggers such as age. The aim of the present study was to investigate the possible interactions between genotype and age and physical activity on risk of obesity.

METHODS

We genotyped PPARGC1A Gly482Ser, in a population-based study comprising 899 women and 902 men aged between 30 and 75 years in Vara, Sweden.

RESULTS

Genotyping revealed that 56% of the males and 57% of the females carried the PPARGC1A 482Ser variant allele. Elderly males (>or=50 years) carrying 482Ser had an increased risk of obesity compared with subjects who were homozygous for the wild-type allele (odds ratio [OR]=1.99, 95% CI 1.14-3.47, p=0.015). The risk was restricted to males with a low leisure-time physical activity level, and was significantly weaker (OR=0.44, 95% CI 0.22-0.87, p=0.018) for the homozygous 482Gly carriers among this subgroup. No association with obesity was found in elderly males with a high level of physical activity, in younger males, or in females of any age group or level of physical activity.

CONCLUSIONS/INTERPRETATION

Our findings confirm that sex and age should be considered when investigating the influence of the PPARGC1A Gly482Ser polymorphism on metabolic disease. The risk of obesity associated with 482Ser is evident only in physically inactive elderly male subjects. Whenever possible, the level of physical activity should be addressed in future studies on disease risk associated with PPARGC1A Gly482Ser.

Obesity and cardiovascular risk factors in type 2 diabetes: results from the Swedish National Diabetes Register

OBJECTIVES

To compare obese with normal and overweight type 2 diabetic patients regarding body mass index (BMI) and cardiovascular risk factors, and to analyse changes in weight versus risk factors.

DESIGN AND SETTING

A cross-sectional study of 44 042 type 2 patients, and a 6-year prospective study of 4468 type 2 patients.

RESULTS

Obese patients (BMI > or = 30 kg m(-2)), 37% of all patients, had high frequencies of hypertension (88%), hyperlipidaemia (81%) and microalbuminuria (29%). Only 11% had blood pressure <130/80 mmHg. Their ratio of triglycerides to HDL cholesterol was considerably elevated, whilst the mean total and LDL cholesterol were similar as in normal weight subjects. Obese patients had elevated odds ratios for hypertension, hyperlipidaemia and microalbuminuria: 2.1, 1.8 and 1.4 in the cross-sectional study, similarly confirmed in the prospective 6-year study. BMI was an independent predictor of these risk factors (P < 0.001), although only slightly associated with HbA1c and not with total or LDL cholesterol. A change in BMI during the prospective study was related to a change in HbA1c in patients treated with diet and oral hypoglycaemic agents (OHAs) but not with insulin. In all patients, an increase in BMI was related to the development of hypertension, and a change in BMI to change in blood pressure, also mostly confirmed when treated with diet, OHAs or insulin.

CONCLUSIONS

The high frequencies of risk factors in obese type 2 patients implies an increased risk of cardiovascular disease and the need for therapeutic measures. The paradox that hypoglycaemic treatment accompanied by weight gain may increase cardiovascular risk factors seems to be verified here concerning hypertension but not concerning microalbuminuria.

Role of the FOXC2 -512C>T polymorphism in type 2 diabetes: possible association with the dysmetabolic syndrome

OBJECTIVE

Overexpression of the human transcription factor FOXC2 gene (FOXC2) protects against insulin resistance in mice and a common FOXC2 polymorphism (-512C>T) has been suggested to be associated with insulin resistance in humans. Here, we addressed the potential role for FOXC2 as a candidate gene for type 2 diabetes and associated phenotypes.

MATERIALS AND METHODS

A case-control study was performed in 390 type 2 diabetic patients and 307 control subjects. The number of patients was increased to a total of 768 subjects for further study of phenotypic differences relating to the dysmetabolic syndrome relative to genetic variation. The FOXC2 -512C>T polymorphism was genotyped by a restriction fragment length polymorphism PCR assay.

RESULTS

FOXC2 -512C>T allele and genotype distribution did not differ between patients with type 2 diabetes and control subjects, but the C/C genotype was associated with increased body mass index (BMI, kg/m2) (Pa=0.03) among type 2 diabetic patients. The FOXC2 -512C>T polymorphism was a significant independent predictor of BMI (P=0.001) in a multiple regression model including age, gender and affection status. We found no significant association with type 2 diabetes-related metabolic parameters but that the C-allele (P=0.01) and C/C and C/T genotypes (P=0.03) were significantly over-represented in type 2 diabetic males with a concomitant diagnosis of dysmetabolic syndrome.

CONCLUSION

We conclude that FOXC2 is associated with obesity and metabolic deterioration but does not contribute to an increased risk for type 2 diabetes.

Characterization of the human skeletal muscle glycogen synthase gene (GYS1) promoter

BACKGROUND

Impaired activation of the human skeletal muscle glycogen synthase by insulin is typical for type 2 diabetic patients. Regulation of glycogen synthase occurs mainly by phosphorylation/dephoshorylation but little is known whether there also is transcriptional regulation. Therefore we studied transcriptional regulation of the human skeletal muscle glycogen synthase gene (GYS1) and evaluated the effects of insulin and forskolin on the promoter activity.

METHODS

Seven promoter fragments were expressed in C2C12 myoblasts and myotubes and in HEK293 cells, and the luciferase assay was used to determine transcriptional activity.

RESULTS

The highest luciferase activity, 350-fold of the promoterless vector, was obtained with nucleotides -692 to +59 in myotubes (P < 0.001), while the nucleotides -250 to +59 provided the highest, 45-fold, activity in the HEK293 cells (P < 0.001). Longer promoter constructs (nucleotides -971, -1707 and -2158 to +59, respectively) had low promoter activity in both cell types. Forskolin treatment for 24 h resulted in approximately 30% decreased promoter activity in myotubes (P < 0.05). Insulin treatment for 0.5-3 h did not increase GYS1 promoter activity; instead the activity was slightly but significantly decreased after 24 h in myotubes (P < 0.005).

CONCLUSIONS

From our results we conclude that basal GYS1 promoter activity is obtained from the first 250 nucleotides of the promoter, while the nucleotides -692 to -544 seem to be responsible for muscle-specific expression, and nucleotides -971 to -692 for negative regulation. In myotubes, the GYS1 promoter was sensitive to negative regulation by forskolin, whereas insulin did not increase GYS1 transcription.

Pro-opiomelanocortin gene is associated with serum leptin levels in lean but not in obese individuals

OBJECTIVE

Mutations in the pro-opiomelanocortin and melanocortin 4 receptor genes (POMC and MC4R) cause monogenic obesity, and the POMC locus (2p21) has been linked to leptin levels and body mass index (BMI). We searched for monogenic obesity due to mutations in POMC and MC4R among morbidly obese Swedes and studied the association of POMC variants with BMI and serum leptin levels.

DESIGN

MC4R and POMC were screened for mutations in 102 obese Swedish subjects (40+/-11 y, 41.3+/-5.0 kg/m(2)) using the single-strand conformation polymorphism technique. The detected polymorphisms were genotyped in 118 lean control subjects (56+/-11 y, 22.6+/-1.3 kg/m(2)) and studied for association with BMI and serum leptin levels.

RESULTS

No cases of monogenic obesity due to mutations in POMC or MC4R were identified and none of the four common POMC polymorphisms (RsaI, ins56, Glu188Gly and C8246T) were associated with obesity. Lean carriers of the C8246T CC-genotype had higher serum leptin levels compared to CT or TT carriers (9.7+/-6.6 vs 6.7+/-4.4 microg/l, P=0.003 for leptin levels adjusted for age, sex and BMI in regression analysis), especially lean females (P=0.004) and lean female carriers with the C8246T(CC)/RsaI(--or +-) genotype combinations (P<0.0005). Neither the C8246T CC-genotype nor the C8246T(CC)/RsaI(--or +-) were associated with serum leptin levels in obese subjects.

CONCLUSIONS

Monogenic forms of obesity due to mutations in POMC and MC4R are rare in Swedish obese patients. Polymorphisms in POMC are associated with variation in serum leptin levels within the normal range in healthy lean but not in obese individuals.

SOCS-3 is involved in the downregulation of the acute insulin-like effects of growth hormone in rat adipocytes by inhibition of Jak2/IRS-1 signaling

One of the long-term effects of growth hormone (GH) in adipocytes is to maintain a state of refractoriness to insulin-like effects, a refractoriness which otherwise declines within a few hours of GH starvation. Here, we examined differences in GH signaling and the possible role for the recently identified family of suppressors of cytokine signaling (SOCS) proteins in the transition between the refractory and the responsive states in rat adipocytes. The ability of GH to stimulate lipogenesis and tyrosine phosphorylation of the GH receptor (GHR), Janus kinase 2 (Jak2), insulin receptor substrate-1 (IRS-1) and -2 (IRS-2) was greatly reduced in refractory as compared to responsive primary rat adipocytes. However, phosphorylation of Signal Transducer and Activator of Transcription 5 (Stat5) was not affected. SOCS-3 and CIS mRNA levels were significantly higher in refractory compared to responsive cells and could be induced by GH, whereas the level of SOCS-2 mRNA was unchanged. With overexpression of GHR, Jak2 and IRS-1 along with each of these SOCS proteins in human A293 cells, we could demonstrate that both SOCS-1 and SOCS-3 completely inhibited the GH-stimulated tyrosine phosphorylation of IRS-1, whereas SOCS-2 and CIS did not. Our data suggest that GH induces refractoriness to the insulin-like effects in a negative-feedback manner by inhibiting GH-induced GHR/Jak2/IRS-1/IRS-2 phosphorylation through upregulation of SOCS-3, which almost completely blocks Jak2 activation.

Characterization of a naturally occurring mutation (L107I) in the HNF1 alpha (MODY3) gene

AIMS/HYPOTHESIS

Maturity onset diabetes of the young type 3 (MODY3) is a monogenic form of diabetes mellitus caused by mutations in the gene encoding for hepatocyte nuclear factor 1 alpha, HNF1 alpha. In this study we have examined the in vivo and in vitro effects of a mutation (L107I) outside the DNA binding and dimerization domains in the N terminal part of the HNF1 alpha gene.

METHODS

Beta-cell function of the affected family members was assessed by an oral glucose tolerance test. Functional tests were carried out to explain the role of the mutation in vitro by transcriptional activity assay, Western blotting, DNA-binding assays and subcellular localization experiments.

RESULTS

Affected family members showed an 86% decreased insulin response to glucose when compared to age-matched healthy control subjects. In vitro the mutation showed a 79% decrease in transcriptional activity as compared to wild type HNF1 alpha in HeLa cells lacking HNF1 alpha. The transcriptional activity was not suppressed when the mutant was co-expressed with wild type HNF1 alpha suggesting that the decreased activity was not mediated by a dominant negative mechanism. The L107I/HNF1alpha protein showed normal nuclear targeting but impaired binding to an HNF1 alpha consensus sequence.

CONCLUSION/INTERPRETATION

Our results suggest that the L107I substitution represents a MODY3 mutation which impairs beta-cell function by a loss-of-function mechanism.

Differential phosphorylation of Janus kinase 2, Stat5A and Stat5B in response to growth hormone in primary rat adipocytes

In vitro growth hormone (GH) stimulation of Janus kinase 2 (Jak2) tyrosine phosphorylation and activation has been detected in rat adipocytes where GH exerts both chronic diabetogenic and acute insulin-like effects but not in adipocytes where only chronic diabetogenic effects are exerted. The 95 kDa transcription factor Stat5, which is tyrosine phosphorylated in response to GH in both cases, is here identified as the 5A-isoform. Stat5B was not tyrosine phosphorylated in response to GH in adipocytes but subject to a gel supershift indicating regulation by serine and/or threonine phosphorylation. The differential tyrosine phosphorylation of these proteins suggests involvement of a kinase other than Jak2 in Stat5A activation. However, in adipocytes where GH exerts both diabetogenic and insulin-like effects, and both Jak2 and Stat5A were activated, their phosphorylation kinetics and downregulation of tyrosine phosphorylation were almost identical. We conclude that Stat5A is important for the diabetogenic actions of GH and that Jak2 still is the most probable candidate kinase for Stat5A in primary adipocytes.

Effects of tyrosine kinase inhibitors on tyrosine phosphorylations and the insulin-like effects in response to human growth hormone in isolated rat adipocytes

Recent data suggest involvement of the Janus tyrosine kinase-2 (JAK2) in human GH-induced tyrosine phosphorylation of the GH receptor and the insulin receptor substrates 1 and 2 (IRS-1 and IRS-2), leading to activation of the phosphatidylinositol 3-kinase and the acute insulin-like effects in primary rat adipocytes. To investigate the functional role of this kinase, we screened a number of tyrosine kinase inhibitors for their ability to inhibit three rapid effects of GH on primary adipocytes: increased lipogenesis, inhibition of noradrenaline-induced lipolysis, and promotion of JAK2 tyrosine phosphorylation. Only staurosporine was found to inhibit all three effects. The inhibition of lipogenesis and antilipolysis exhibited the same staurosporine dose dependency (IC50, approximately 40 nM) as inhibition of JAK2 and IRS-1 tyrosine phosphorylation as well as binding of the p85 subunit of phosphatidylinositol 3-kinase to IRS-1 and IRS-2. The unidentified cytosolic tyrosine-phosphorylated protein pp95, in contrast, was not affected, suggesting that it is not phosphorylated primarily by JAK2. Protein kinase C does not seem to be directly involved in the insulin-like effects, because the selective protein kinase C inhibitor calphostin C had no effect at levels up to 100 nM above which unspecific cellular effects occurred. Methyl-2,5-dihydroxy cinnamate inhibited GH-induced lipogenesis from [3-3H]glucose and nonstimulated lipogenesis from [2-14C]-pyruvate and [3H]acetate, but was without effect on GH-induced 2-deoxy-D-[1-3H]glucose uptake, JAK2 phosphorylation and antilipolysis, suggesting unspecific effects on mitochondrial metabolism rather than a direct effect on the GH-mediated signal. Tyrphostin 25 and herbimycin A had no effect on any of the parameters studied, except for a slight increase in JAK2 phosphorylation in response to tyrphostin 25. In summary, these data support the role for JAK2 in mediating the insulin-like effects of GH in adipocytes.

Tyrosine phosphorylation of the growth hormone (GH) receptor and Janus tyrosine kinase-2 is involved in the insulin-like actions of GH in primary rat adipocytes

The nature of tyrosine phosphorylations induced by GH in relation to the insulin-like metabolic effects in primary rat adipocytes was investigated. Unlike other cells, e.g. 3T3-F442A fibroblast, in which GH is believed to initiate cell differentiation through activation of the Janus tyrosine kinase-2 (JAK2), the adipocytes are metabolically active and fully differentiated cells that do not proliferate. Thus, it cannot be assumed that the same molecular mechanisms relay the acute insulin-like effects of GH. In adipocytes responsive to these effects, we found that GH induced tyrosine phosphorylation of a 114-kilodalton membrane protein, identified as the GH receptor, and a 130-kilodalton cytosolic protein, identified as JAK2. In contrast, these phosphorylations were not seen in adipocytes refractory to these effects of GH. The GH concentration dependency (ED50,1-2 nM) of these phosphorylations coincided with the increase in lipogenesis and the decrease in noradrenaline-induced lipolysis caused by the hormone. In analogy with the effects of insulin, the onset of phosphorylation was rapid (t1/2, < 1 min) and preceded the metabolic responses. The observations that a small fraction of the receptor pool became tyrosine phosphorylated and that the level of phosphorylation induced by GH decreased at higher GH concentrations agree with the concept that GH-induced dimerization of the receptor is necessary for signal transduction. We conclude that tyrosine phosphorylation of JAK2 and the GH receptor seems to be involved in the signal transduction mechanism leading to the insulin-like effects of GH in adipocytes. Importantly, the signal pathways for GH and insulin clearly differ at the receptor level, but seem to converge at or before the level of insulin receptor substrate 1 or 2 phosphorylation that has been shown to occur in response to both of these hormones.

Evidence for the key role of the adipocyte cGMP-inhibited cAMP phosphodiesterase in the antilipolytic action of insulin

Enhancement of cAMP degradation by increased cGMP-inhibited cAMP phosphodiesterase (cGI-PDE) activity is thought to be an important component of the mechanism whereby insulin counteracts catecholamine-induced lipolysis in adipocytes. In this study the selective cGI-PDE inhibitor OPC3911 was used to evaluate this role of cGI-PDE activation in intact rat adipocytes with special reference to changes in cAMP levels measured as cAMP-dependent protein kinase (cAMP-PK) activity ratios. OPC3911 completely blocked (IC50 = 0.3 microM) the maximal inhibitory effect of insulin on noradrenaline-induced lipolysis and the net dephosphorylation of hormone-sensitive lipase and other intracellular target proteins for insulin action, whereas insulin-induced lipogenesis was not changed. The effect of OPC3911 on cAMP-PK activity ratios at different levels of lipolysis achieved by noradrenaline stimulation revealed that the reduction of cAMP-PK caused by 1 nM insulin was completely blocked by 3 microM OPC3911. The effect of OPC3911 was not due to an excessive increase in cellular cAMP resulting in 'supramaximal' lipolysis unresponsive to insulin. These data demonstrate that reduction in cAMP levels by the activation of cGI-PDE may be sufficient to account for the antilipolytic action of insulin.

Growth hormone stimulates the tyrosine phosphorylation of the insulin receptor substrate-1 and its association with phosphatidylinositol 3-kinase in primary adipocytes

Insulin receptor substrate-1 (IRS-1) is tyrosine-phosphorylated in response to insulin resulting in association with and activation of phosphatidylinositol 3-kinase (PI 3-kinase), thereby initiating some of the effects of insulin. We have recently shown that the insulin-like effects of growth hormone (GH) in adipocytes can be inhibited by the selective PI 3-kinase inhibitor wortmannin (Ridderstråle, M., and Tornqvist, H. (1994) Biochem. Biophys. Res. Commun. 203, 306-310), suggesting a similar role for PI 3-kinase in GH action. Here we show that IRS-1 is tyrosine-phosphorylated in a time- and dose-dependent manner in response to GH in primary rat adipocytes. This phosphorylation coincided with the extent of interaction between IRS-1 and the 85-kDa subunit of PI 3-kinase as evidenced by coimmunoprecipitation. Stimulation with 23 nM GH increased the PI 3-kinase activity associated with IRS1 4-fold. Our data suggest that GH-induced tyrosine phosphorylation of IRS-1 and the subsequent docking of PI 3-kinase are important postreceptor events in GH action. The mechanism for the phosphorylation of IRS-1 induced by GH is unknown, but involvement of JAK2, the only known GH receptor-associated tyrosine kinase, seems possible.

PI-3-kinase inhibitor Wortmannin blocks the insulin-like effects of growth hormone in isolated rat adipocytes

The effect of wortmannin, a selective phosphatidylinositol 3-kinase inhibitor, on the insulin-like effects of growth hormone in isolated adipocytes from rat was investigated. Wortmannin inhibited both the lipogenic and the antilipolytic effects (IC50 approximately 20 nM) with no effect on [125I]-growth hormone binding to the adipocytes. These data suggest that phosphatidylinositol 3-kinase might play an important role in the insulin-like actions of growth hormone.

Essential role of phosphatidylinositol 3-kinase in insulin-induced activation and phosphorylation of the cGMP-inhibited cAMP phosphodiesterase in rat adipocytes. Studies using the selective inhibitor wortmannin

Incubation of rat adipocytes with wortmannin, a potent and selective phosphatidylinositol 3-kinase (PI 3-kinase) inhibitor, completely blocked the antilipolytic action of insulin (IC50 = 100 nM), the insulin-induced activation and phosphorylation of cGMP-inhibited cAMP phosphodiesterase (cGI-PDE) as well as the activation of the insulin-stimulated cGI-PDE kinase (IC50 = 10-30 nM). No direct effects of the inhibitor on the insulin-stimulated cGI-PDE kinase, the cGI-PDE and the hormone-sensitive lipase were observed. These data suggest that activation of PI 3-kinase upstream of the insulin-stimulated cGI-PDE kinase in the antilipolytic insulin signalchain has an essential role for insulin-induced cGI-PDE activation/phosphorylation and anti-lipolysis.

cAMP-dependent protein kinase activation mediated by β3-adrenergic receptors parallels lipolysis in rat adipocytes

Catecholamine-induced lipolysis is chiefly mediated through the recently characterized beta 3-adrenergic receptor (AR) in rat adipocytes. Discrepancies between the ability of beta 3-AR agonists to stimulate adenylyl cyclase and the resulting lipolysis were recently reported. cAMP-dependent protein kinase (A-kinase) activation induced by these agonists was compared to lipolysis. Agonist potencies were similar for A-kinase activity ratios and lipolysis. The same A-kinase activity ratio to lipolysis relationship was found for the beta 3-AR agonists tested.